Most people who suck at their jobs can be fired. Teachers, thanks to unions, really can't. So tax payer's are forced to continue to pay in, yet not get much return on the 'investment.' Not saying all teachers are bad, but a decent number of them are. As a parent you don't get to shop for teachers, or schools; you're stuck with whatever happens to come up. Even if you /really/ dislike a teacher, you've got almost no redress if there doesn't happen to be room in another class.
I had to spend half a year being taught by a teacher that publicly accused me of telling a friend to commit suicide. I had given him a mix tape that included the song Suicide Solution by Ozzy. The teacher took it as an encouragement (the song is actually the opposite.) The teachers comment was not only in the news paper but on TV. The fucked up part, that teacher became the principle of the school three years later. Thank's teachers union \o/
I had a nasty, nasty bulldyke of a gym teacher for three years who made life misery for me and a number of other girls who weren't her favorites. She was a miserable ***** but I didn't turn against the teaching profession because of it. You ever meet someone nasty and unfair at work? In your local PTA or church group? Some people are like that; they can pop up in a school, as well.
The sad thing is, a lot of teachers agree that the tenure laws allow burnt out teachers to stay too long. The reason for the law, though, isn't to protect lousy teachers. It goes straight back to the salary issue. School boards looking at a tight budget and a loudly protesting group of tax payers would fire any teacher about to go up in the pay scale. Whether someone is a good teacher or not can be very subjective and if you look closely enough with a dark enough pair of glasses, you will find reasons whether they exist or not. Some schools here are famous for hiring new teachers for two years and then when they would receive tenure and get a pay raise, the school doesn't renew and hires some other brand new "cheap" teachers.
I agree with you that firing an incompetent teacher should not be next to impossible. Just keep in mind that "incompetent" can be largely in the mind of the beholder, or a personality issue, as it was with you.